This invention relates generally to rotary punches and more particularly to rotary punches with releasable punch elements.
The use of rotary punches to perforate a web of material, such as paper or cardboard, is well known. A problem with rotary punches has been that the punch elements frequently are broken or become dulled in continuous use and need to be replaced. Because not all of the punch elements require replacement at the same time, some punch wheels are constructed to releasably hold the punch elements so that they may be individually removed and replaced. Examples of such constructions are shown in U.S. Pat. Nos. 4,688,459 (Osborn et al.), 4,604,931 (Bastian et al.), 3,828,632 (Grano), 4,558,620 (Wallis), 4,174,648 (Wallis) and 4,377,100 (Wallis), each of which generally discloses punch wheel having a pin or ball which is received in a cavity in the punch wheel near each punch element. The pin or ball is movable and spring biased against the punch element to hold the punch element in the wheel. The punch elements are released by pulling on the punch element itself, inserting a tool into the punch wheel to disengage the pin or ball from the punch, or pressing a button on the punch wheel to release the punch element. However, these designs have one or more drawbacks, including complexity of construction and failure to positively lock the punch elements in the punch wheel while still allowing damaged punch elements to be removed with a minimum of effort.